The present invention relates to a power transistor device, particularly to effective technology to be utilized in so-called IC igniter in an ignition device of an internal combustion engine.
In the prior art, a Zener diode is provided between collector and base of a bipolar transistor device used in an ignition device (IC igniter) of a multicylinder internal combustion engine to be mounted on an automobile, in order to stabilize voltage of a primary coil applied to each cylinder. Reverse voltage generated in a primary coil is stabilized by Zener voltage of the Zener diode. Darlington transistor circuit is used as a power transistor device as above described. U.S. Pat. No. 4,618,875 discloses a power transistor device using a Darlington transistor circuit.